In standard ignition systems in automobiles there is provided a heat sensing switch, generally in the form of a thermocouple, which closes when the water temperature of the engine heats to a temperature of approximately 220.degree. F., and this results in a red light on the dashboard being energized to indicate that the engine is overheating. As the result of the addition of antismog devices in automobiles, engines overheat much more frequently in hot, humid weather than in the past. This type of overheating has become a severe problem in rental cars where the lessee is not as careful with the equipment as he probably would be with his own. In any event, rental car owners have experienced substantial expenses in excessive repairs to overheated motors which were driven after the warning lights indicated that they were overheating.
Because of the great expense involved since the advent of the antismog devices, attempts have been made to eliminate the overheating problem. This problem has been solved by the present invention which, in addition to warning signals, provides means to shut off the engine before it overheats enough to cause damage.
In view of the automobile theft problem, the present invention has been adapted to be applied with the addition of an antitheft switch. The antitheft switch, like the heat sensing switch, is a normally open switch but is hand operated, whereas the heat sensing switches are automatically closed at a predetermined temperature. The antitheft switches may be installed independently of the heat sensing switch or may be installed in parallel with the heat sensing switch, in which situation they are independently operable to shut off an internal combustion engine.